Liebert can't attain setpoint when outdoor is low...

[alexb]

My Server room has a ceiling-mount Liebert unit. Facilities person says its a Glycol system with a drycooler on the roof. When the ambient outdoor temp is higher than 50, it can maintain 73setpoint just fine. However on the east coast over the last month we've been having below normal temps, below freezing for a high, and lows around 10-15.

During this cold period, the Liebert can't even maintain 76. One facilities person says that the system is low on charge, where low outdoor temp prevents proper pressure being attained in the evaporator. Another guy says that there's so little load on the unit, that I ice the coil over if the compressor runs too much.

What do the experts think? I vote for low charge. Higher outdoor ambient means higher evap. pressure, means cooler temps in my server room. Also, a "hot-gas-bypass" was mentioned, to keep temperatures up in the condenser.

[The Doctor]

glycol????....hgbp in condenser???? i'd like to know which
the condensers with lee temp features run great until the COLDest days, then if a little low, your suction will drop off entirely until the outdoor temp climbs just a bit.
i hate to wait for godot, but...
it depends, and from the sounds of it, it may depend on a lot...
you can e-mail me if you're in the vicinity of balto/dc/northern va, because i would then recommend some great folks for a service call, liebert certified, I won't mention the name unless you e-mail.

[Airmechanical]

My Server room has a ceiling-mount Liebert unit. Facilities person says its a Glycol system with a drycooler on the roof.what do the experts think? I vote for low charge. Also, a "hot-gas-bypass" was mentioned, to keep temperatures up in the condenser.

does this mean you have not been on the roof yet, the experts

think you need to go on the roof and give a little more info!

i take it this is a minimate?

you are getting your main info from a maintanance man, you are the hvac tech!



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[hvac_superman]

Is this maybe a glycool system? They have a 3-way valve that redirects the cool glycol thru a cooling coil in the indoor unit to utilize free cooling in the cool months. If that is what you have there could be issues with the 3-way valve.

[alexb]

I'll relay the info on the three-way valve to my facilities guy. --I'm not an HVAC person; I'm just someone who's getting yelled at from his management, "It's too warm in the server room, do something about it!"

How about an ambient kit for the outside unit? That would keep temps & pressures up a bit.

Our facilities person is HVAC (NATE) certified, but I bet I could find alot of info here, from people with Liebert experience, that I could pass along.

Also, I'm about to put nearly 10,000BTU more into this room, so I'm looking for opinions on how to prevent an 80degree server room next winter.

[matt8085]

The last water cooled Leibert with dry cooler that I worked on had a water valve that fed the condensor accordingly depending on refrigerant head pressure. I've also seen circuit setters that are just a fixed flow of water regaurdless of the temp. The fans on the dry coolers are likely staged on leaving water temp. I wouldn't go adding heat to that room unless you have a load calculation done to determine if your current system is sufficient.

[Airmechanical]

I'm just someone who's getting yelled at from his management, "It's too warm in the server room, do something about it!"
How about an ambient kit for the outside unit?Our facilities person is HVAC (NATE) certified

(NATE) does not have a certification for leibert style equipment!



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[Randy S.]

Put your gauges on it. Know what type of system you have. There are also remote condensers in the Liebert line, both Lee-Temp and P-66 types.

I'd guess you're running low head from the glycol loop being too cold or poorly controlled. Check the fan switch settings on the dry cooler. Some Lieberts have a bypass around the water reg valve, and it may have been left open.

Someone may have jacked the water reg valve way open last summer or something like that. Set it for around 225 on R-22.

[HVACJOEK]

Alex post the model numbers of your liebert units (indoor and outdoor) then we can see what you have there.

[Balibe]

Also, I'm about to put nearly 10,000BTU more into this room, so I'm looking for opinions on how to prevent an 80degree server room next winter.

Before you go adding more equipment to this room you may want to do a load analyst. Even if all issues are fixed with the unit, it may not be sized for the additional 10,000btu [almost a ton of cooling].

I have seen it before. The original unit was correctly sized for the original load. Over time they slowly add equipment to the room and before they know it the unit is undersized for the room/equipment.

Liebert does their own certifications for their equipment, not saying that no one can work on them. With the issues you have and different diagnoses/recommendations, you may want to call Liebert and get a list of local companies that are certified.

[heatingman]

How about an ambient kit for the outside unit? That would keep temps & pressures up a bit.

Our facilities person is HVAC (NATE) certified, but I bet I could find alot of info here, from people with Liebert experience, that I could pass along.

.

lieberts usually come from the factory with cold weather controls ie lee heaters, fan cycling, and head pressure regulators with bypass valves, or a combo of all three. Sounds to me like your facilities guy is in over his head, lieberts make a fairly complex system, lots of bells and whissles, and computerized everything. You need someone familliar with liebert, b/c guessing at problems using the facilities guy, can cost alot more in computer equiptment then it will cost for a service call to a profesional

[The Doctor]

Before you go adding more equipment to this room you may want to do a load analyst. Even if all issues are fixed with the unit, it may not be sized for the additional 10,000btu [almost a ton of cooling].

I have seen it before. The original unit was correctly sized for the original load. Over time they slowly add equipment to the room and before they know it the unit is undersized for the room/equipment.

Liebert does their own certifications for their equipment, not saying that no one can work on them. With the issues you have and different diagnoses/recommendations, you may want to call Liebert and get a list of local companies that are certified.

not to hijack, but if I had a nickel for every time the site contacts said the units just don't keep up like they used to and you find a new jukebox, (disk array), or a couple of new sharks.
oh they been in here for at least 2 months???!!
thanks for the update, sign here..

[incontrol]

I'll chime in here because I did have one that was a mess. Same symtoms as above (but they put sprinklers on it in the summer to cool it down). It had glycol to the roof and I was getting poor heat transfer. After scratchin' my head a while it dawned on me - they had it piped backwards. The glycol should be piped counterflow, meaning the hot entering glycol goes in the top and leaves the bottom where the fresh air is coming in. They piped the hot in the bottom so the rest of the passes got the heated air. When I went back to the shop and explained it the manager admitted they originally filled the system with auto antifreeze. That is a no-no because silicates lined the copper walls and ruin the heat transfer. Double whammy! Good luck!